RF调试经验和原理

1、RF调试经验和原理三旗硬件部 王健2007.07. 17Comment RF 器件的选择 RF layout 注意事项 如何调试RF性能 RF 主要的使用仪器 AT 命令的使用RF 器件的选择RF的主要器件分类 有源器件 放大器 (多种)TXCO 无源器件滤波器 耦合器 功分器 混频器 衰减器 双功器天线陷波器如何选择RF器件 根据RF系统的需要选择合理的器件 性能 价钱 替代性环境对有源RF器件性能的影响 偏置 温度 负载主要的RF器件供应商 放大器 FujitsuMitsubishi NECAMcomHittiteRFMDANADIGICSInfineonMaxiam AgilentPA

2、电路LNA电路放大器电路传输线特性阻抗50ohm75ohm300ohmZ0=根号(L/C)RF单位运算相对单位量dBdBcdBidBd绝对单位量dBvdBmdBm=dBm-(+)dBm 错误 如30dBm+30dBm=33dBmdB=dBm-(+)dBm 正确dBm=dBm-(+)dB 正确dB=dB-(+)dB 正确RF走线规则偏置上串大小电容DC Choke走线RX 走线TX 走线微带线四周为和打地孔?RF阻抗线下为何挖层偏置上串大小电容偏置上串大小电容偏置上串大小电容DC Choke走线RF仿真软件主要用于matching,VCO,power,Gain,Noise figure,等高频有

3、源仿真ADS WMO主要用于天线仿真,以及EMI,以及如手指filter,耦合器,等高频无源仿真ANsoftHFSSSonnetCSTRX Sensitivity tuningSystem NFLNA NFGain Block Gain and PowerSystem modulation typeLink budgetHarmonicIM3SpurSensitivity EquationInput signal (Si)Input noise (Ni)Output signal (So)Output noise (No)System Output Signal to Noise Ratio

4、(SNRo dB) =10log(So/No)System Input Signal to Noise Ratio (SNRi dB)=10log(Si/Ni)Noise Figure ( NF dB)=SNRi-SNRoSensitivity (dBm)=SNRo(dB)+NF(dB)+kT0 (dBm)+ B(dB)kT0 (dBm)Standard input noiseDynamic Range (dB)=Sensitivity+ Output PowerTX output power tuningPA P1dBDriver Amplifier P1dBMixer input P1dB

5、Lo powerOutput power lossHarmonicIM3SpurTX output power tuningWhy we must keep PA output power linear.如果PA输出线性度不好 会影响到信号的 AM PM导致输出信号失真. AM to AM and AM to PM ConversionIQBER will increase due to magnitude and phase migrationsof the IQ constellation when amplifiers gain is compressed. AM/PMAM/PMAM/A

6、MAM/AMSpecifications of RF AmplifiersThird-order intercept point, PIP3(OIP3)PIN(dBm)POUT(dBm)PIP3(dBm)IMD(dBc)X2XIM3(dBm)13PIP3 = POUT+IMD/2FundamentalIM3XSpecifications of RF Amplifiers Nonlinear Distortion of Amplifier VINVOUTPower series expansion of amplifier outputVOUT=K0 + K1 VIN + K2 VIN2 + K

7、3 VIN3 +.VINVOUTVIN =A cos w1t DC offsetGain compression (K3 0)VOUT =(K0+0.5 K2 A2)+(K1 A+ 0.75 K3 A3)cos w1t+0.5 K2 A2 cos 2w1t + 0.25 K3 A3 cos 3w1t +Second harmonic termThird harmonic termSingle-Tone Harmonic Analysis VIN =A cos w1t + A cos w2t VOUT =(K0+ K2 A2)DC +(K1 A+ 3/4 K3 A3)(cos w1t+ cos

8、w2t)1st +1/2 K2 A2 cos 2w1t+ cos 2w2t2nd +1/4 K3 A3 cos 3w1t + cos 3w2t 3rd +1/2 K2 A2 cos(w2+w1)t+ cos(w2-w1)tIM2 +3/4 K3 A3 cos(2w1-w2)t+ cos(2w2-w1)tIM3 +Two-Tone Intermodulation Analysisw2w12w2-w12w22w1-w2w2-w1w2+w12w1Pout (dBm)FreqIM2IM3IM3IMD(dBc)=POUT(dBm)-IM3(dBm)PoutSpectrum of Spurious Out

9、put SignalsRF调试中可能的问题SMT问题干扰问题器件选择问题Layout问题为何要做阻抗匹配防止EMC EMI加强能量的传输频率波长 趋肤深度 对照表 频率 /2 趋肤深度 10Hz 30,000km 4,800km 820mil 60Hz 5,000km 800km 340mil 100Hz 3,000km 480km 260mil 400Hz 750km 120km 130mil 1kHz 300km 48km 82mil 10kHz 30km 4.8km 26mil 100kHz 3km 480m 8.2mil 1MHz 3000m 48m 2.6mil 10MHz 30m

10、4.8m 0.8mil 100MHz 3m 0.48m 0.3mil 1GHz 30cm 4.8cm 0.08mil 10GHz 3cm 4.8mm 0.03milRF 主要的使用仪器8960 CMU200Network analyzerSpectrum analyzerPower meterNoise figure meterFrequency meterSignal generatorOscillatorTime Domain Reflector (TDR)RF 测试辅助设备和配件Connector (SMA,SMB,N type) male and femaleCable (50ohm,75ohm,300ohm)Calibration kitAttenuator (SMA or Pai resistance)Filter CouplerPower dividerPower detect